Commas before FANBOYS subordinating conjunctions??

[NoonarAgain]

I've been looking at some on line resources for teaching punctuation and grammar and would like to check a couple of things.

Is it correct to use a comma beforethe FANBOYS conjunctions (as in the sentences below)?

I might get a pizza, or I might get a burger.
I would like a dog, but my brother would prefer a cat.
Tom ran as fast as he could, yet Tom won the race.

I am asking because I think I disagree with what it is saying online.

TIA

Quick "rule" commas are used to separate clauses and would be placed before and, but, for, nor, or, yet

These grammar tutorial video's are awesome.

www.khanacademy.org/humanities/grammar

Assuming there are two Toms otherwise the last sentence wouldn't make sense, I wouldn't put a comma in any of them.